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Old 03-23-2006, 05:42 PM   #1
Hurley 2.5 WRS
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Member#: 43916
Join Date: Sep 2003
Chapter/Region: RMIC
Location: Old Town
Vehicle:
2001 Impreza 4.7
Blue Ridge Pearl

Default Check my Math!!!

ok engineers and math majors, check my algebra, and equation for that matter, as i made it up to attain the CR. i need this because the piston dish and my value "D" are different now, and i need a head gasket in the right thickness, or at least close.
may be a little hard to understand, but if you know how and want to help, its easier to write it down

for 8:1 CR ratio.
HG= head gasket thickness in cm
HS= head volume/combustion chamber size in cc
PD= piston dish volume in cc
D= distance the piston comes out of the deck in cm (if it is under, its negative)

Eqn: 8/1 = (((HG-D)*(pi*4.6^2))+HS+PD+498.57)/(HS+PD+((HG-D)*pi*4.6^2))

498.57 is the volume of the cylinder made by the stroke: (pi*4.6^2)*7.5

so: 8(HS+PD+((HG-D)*pi*4.6^2)) = ((HG-D)*(pi*4.6^2))+HS+PD+498.57

do algebra...... i got:

HG = (-(HS+PD)+71.2245)/(pi*4.6^2))+D
\/


HG = -(HS+PD)/(pi*4.6^2) + 7.5/7 + D

thanks guys
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Old 03-23-2006, 05:52 PM   #2
Matt Monson
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'73 914 and 2012 BRZ

Default

Just put the damned v7 block in the car with an EJ205 gasket and get on with it already!
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Old 03-23-2006, 06:11 PM   #3
Hurley 2.5 WRS
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2001 Impreza 4.7
Blue Ridge Pearl

Default

Quote:
Originally Posted by Matt Monson
Just put the damned v7 block in the car with an EJ205 gasket and get on with it already!


so, anyone?
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Old 03-23-2006, 06:31 PM   #4
Matt Monson
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Join Date: Jan 2000
Chapter/Region: RMIC
Location: Teh Ghetto Garage, CO
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99 2.5RS, '85 911
'73 914 and 2012 BRZ

Default

I'm done doing math for people. After I started publishing numbers for a bunch of different combos, I started getting all these PM asking me to calculate CR's for people. Free bump to get someone to do the math.

BTW, there are some very good online calculators that will do it for you...
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Old 03-23-2006, 06:42 PM   #5
Hurley 2.5 WRS
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Location: Old Town
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2001 Impreza 4.7
Blue Ridge Pearl

Default

well, im pretty sure the math is correct, i just want someone to check the algebra.

ps, possible link to an online calculator for cr?
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